Furnace not working right with Aprilaire


  #1  
Old 11-15-03, 08:25 PM
Tim_123
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Furnace not working right with Aprilaire

If I leave the Aprilaire unit turned off, the furnace runs fine. With the Aprilaire on, the furnace comes on for 10-15 minutes then shuts off for a few minutes and starts up again, repeating this process until thermostat temp is reached.

The local contractor is not much help. He was out to service it recently and had it working OK, but he missed the thing about the Aprilaire, I figured that out for myself. He says that this is lousy and quirky model and recommends replacing it.

Its a Ruud 90+ furnace, 11 years old, replaced aluminum heat exchanger 4 years ago, has had lots of new parts including a circuit board. I live in N. Illinois. Non-digital thermostst. The furnace worked well last season, and this problem started this fall. A contractor installed a new limit switch in the spring, at the end of the last heating season.

Any ideas?
 
  #2  
Old 11-16-03, 04:42 AM
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Where is the power or control wire tied to for the April Air?

If you use the low voltage, taking it off of the R or W on the furance, you may be robbing the power, and system then start acting funny.
 
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Old 11-16-03, 08:51 AM
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Question Run time

Id go back to that new limit control here??? Why????? I dont think I have ever replaced a limlt control. Fan limit yes a lot, cause the fan side went out, limit side no. Did he put in the right length element on this limit control. You could stay there by the furnace and jump out that limit control with the Aprilaire on and see if the furnace runs ok that way. if so look at that limit control. He didnt change any wires when he put the limit in did he?

Be sure and take the jumper back off the limit. ED
 
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Old 11-17-03, 05:37 PM
Tim_123
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Jay, the black wire for the Aprilaire goes to the HUM terminal on the furnace and the white wire goes to a neutral terminal.

Ed, the limit switch was replaced because some of the plastic had become cracked and brittle and it was almost ready to fall out. I don’t believe he did any rewiring for this, he just reconnected the old wires. I don’t know how to read the rating of the switch, one number on it is 200 and a sticker on the furnace call for a limit of 180 degrees.

Additional info left off original posting is that this is an intermittent problem. Sometimes the furnace runs OK with the Aprilaire on, but once it starts to screw up I have to turn the Aprilaire off to get it to run right again. Maybe the problem is with the Aprilaire, it was installed with the furnace 11 years ago and has run OK until this fall. Its a model 550 and there is what looks like an adjusting screw on the valve but I don’t know anything about it. Could the relay or valve for the Aprilaire be the problem?
 
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Old 11-17-03, 08:16 PM
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Tim,

It sounds like it's wired up right.. You have an AMP meter? I would take an AMP reading and see if the coil on the humidfire is taking tooo much amp, and the transformer can't handle it.

If you can live a few days with out the humidfire, I would disconnect it from the furance and see what happens..
 
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Old 11-18-03, 10:47 AM
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Question FURNACE

First let find out why or what made that plastic limit brittle here. Also how can he put a 200o limit there when you say it spec. for 180o. Does the furnace blower motor run like it should all the time? Is the air filter in the furnace clean and has it been clean all the time? ED
 
 

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